1. Field of the Invention
This invention relates generally to an electronic musical instrument and particularly to a musical tone waveform producing apparatus for using in a waveform-reading-type electronic musical instrument.
2. Prior Art
A digital technology in electronic musical instruments is rapidly improved recently. Particularly, a waveform-reading method, in which a musical sound is produced by respectively reading prestored tone-color waveform data and prestored envelope data from a waveform memory and an envelope memory, is popularly used together with a PCM method in the electronic musical instruments.
However, in a conventional musical tone waveform producing apparatus for electric musical instruments, the time length of each of tone-color waveform data is difficult to equalize with that of each of envelope data. In order to achieve a correct time adjustment, the number of bit of envelope data block is necessarily increased so that an envelope control circuit becomes complicated therefor. In addition, there is drawback that if the same envelope data is used when a tone is of high pitch, since a frequency due to frequency information becomes high, the time period of one tone-color waveform data becomes short. Accordingly, a resultant waveform has an undesirable noise component which is caused by the following tone-color waveform data.